In general, a blender is a household appliance which is adapted to be used for processing food, particularly mixing, comminuting, and/or aerating food. To this end, the blender comprises one or more rotatably arranged tools such as whisks or knives for moving through the food. In one known type of blender, which is known as stick blender, a rotatably arranged knife is applied, which usually has two diametrically arranged blades in a more or less flat appearance, like a propeller. Furthermore, a stick blender has a housing for accommodating components of the blender, including means such as a motor for driving the knife, and an elongated, stick-shaped device carrying the knife at an end thereof. The housing is shaped such that it is possible for a user to take hold of the blender in a very convenient manner, and to have a firm grip on the blender during food processing actions. In use, the user inserts the stick-shaped device in a quantity of food, with the knife down, wherein the food is processed as the knife rotates. The user may move the blender during a food processing action, so as to continually change the location of the rotating knife in the food.
In order to avoid injuries of the user and/or damage to an inner surface of a container in which food to be processed is present, it is desirable to have the knife covered as much as possible, however, without deteriorating the functionality of the knife. To this end, a suitable cover is used, which is referred to as tool cage, and which has an opening for allowing the knife to reach the food, but which prevents a user from freely touching the knife. Furthermore, in a more general sense, the use of a tool cage greatly improves the effectiveness of the knife and the performance of the blender. A standard orientation of a stick blender is a vertical orientation with the knife at a downside, and in such an orientation, the tool cage is at a downside of the blender as well, and serves for preventing a user from touching the knife from the side. Normally, the tool cage is shaped like a tapered, hollow cylinder having an open end, like a cup, a bell, a bowl, a tulip, an umbrella, or the like. The tool cage may be removably arranged for cleaning purposes, for example.
A tool cage as mentioned, suitable for use in a hand-held blender or mixer, is known from WO 99/48411. It is noted that in this text, the words “blender” and “mixer” are regarded as equivalents, and that only the word “blender” is used. An inner surface of the tool cage defines a space which is accessible from below via an opening through which food is supplied and discharged during a food processing action. The inner surface has on its circumference individual outwardly extending wall sections for the formation of clearance spaces, wherein the wall sections serve primarily for the diversion, comminution, and/or enhanced mixing of food, while the clearance spaces are used for receiving and discharging the food. Hence, in this design of a tool cage, a cross-section of the tool cage is shaped like an undulating ring, with alternating concave and convex portions.
In U.S. Pat. No. 5,639,034, another tool cage is disclosed, which includes an inner surface having a cross-section which takes the form of a substantially regular polygon with at least five and preferably fifteen sides. On the basis of this particular shape of the inner surface of the tool cage, food materials are comminuted in the tool cage particularly rapidly. After the food impinges against the inner surface, the polygonal profile causes the food to be deflected from the inner surface and to be directed back to the area where the knife is for further comminution.